This reverts commit 6778ff5b21bd8e78c8bd547fd66437cf2657fd9b.
The commit adds up to 100 ms to the boot process, which is not mentioned
in the commit message, and is making up more than 20 % on current
systems, where the Linux kernel takes 500 ms.
[ 0.000000] Linux version 5.11.0-10281-g19b4f3edd5c9 (root@a2ab663d937e)
(gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian)
2.35.1) #138 SMP Wed Feb 24 11:28:17 UTC 2021
[…]
[ 0.106422] smpboot: CPU0: AMD Ryzen 3 2200G with Radeon Vega Graphics
(family: 0x17, model: 0x11, stepping: 0x0)
[…]
[ 0.291257] pci 0000:00:00.2: AMD-Vi: Unable to read/write to IOMMU perf
counter.
[…]
Also, it does not fix the problem on an MSI B350M MORTAR with AMD Ryzen
3 2200G (even with ten retries, resulting in 200 ms time-out).
[ 0.401152] pci 0000:00:00.2: AMD-Vi: Unable to read/write to IOMMU perf
counter.
Additionally, alternative proposed solutions [1] were not considered or
discussed.
[1]:
https://lore.kernel.org/linux-iommu/[email protected]/
Cc: Suravee Suthikulpanit <[email protected]>
Cc: Tj (Elloe Linux) <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Alexander Monakov <[email protected]>
Cc: David Coe <[email protected]>
Cc: [email protected]
Signed-off-by: Paul Menzel <[email protected]>
---
drivers/iommu/amd/init.c | 45 ++++++++++------------------------------
1 file changed, 11 insertions(+), 34 deletions(-)
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 9126efcbaf2c..af195f11d254 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -12,7 +12,6 @@
#include <linux/acpi.h>
#include <linux/list.h>
#include <linux/bitmap.h>
-#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/syscore_ops.h>
#include <linux/interrupt.h>
@@ -257,8 +256,6 @@ static enum iommu_init_state init_state = IOMMU_START_STATE;
static int amd_iommu_enable_interrupts(void);
static int __init iommu_go_to_state(enum iommu_init_state state);
static void init_device_table_dma(void);
-static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
- u8 fxn, u64 *value, bool is_write);
static bool amd_iommu_pre_enabled = true;
@@ -1717,11 +1714,13 @@ static int __init init_iommu_all(struct
acpi_table_header *table)
return 0;
}
-static void __init init_iommu_perf_ctr(struct amd_iommu *iommu)
+static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
+ u8 fxn, u64 *value, bool is_write);
+
+static void init_iommu_perf_ctr(struct amd_iommu *iommu)
{
- int retry;
struct pci_dev *pdev = iommu->dev;
- u64 val = 0xabcd, val2 = 0, save_reg, save_src;
+ u64 val = 0xabcd, val2 = 0, save_reg = 0;
if (!iommu_feature(iommu, FEATURE_PC))
return;
@@ -1729,39 +1728,17 @@ static void __init init_iommu_perf_ctr(struct amd_iommu
*iommu)
amd_iommu_pc_present = true;
/* save the value to restore, if writable */
- if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false) ||
- iommu_pc_get_set_reg(iommu, 0, 0, 8, &save_src, false))
- goto pc_false;
-
- /*
- * Disable power gating by programing the performance counter
- * source to 20 (i.e. counts the reads and writes from/to IOMMU
- * Reserved Register [MMIO Offset 1FF8h] that are ignored.),
- * which never get incremented during this init phase.
- * (Note: The event is also deprecated.)
- */
- val = 20;
- if (iommu_pc_get_set_reg(iommu, 0, 0, 8, &val, true))
+ if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false))
goto pc_false;
/* Check if the performance counters can be written to */
- val = 0xabcd;
- for (retry = 5; retry; retry--) {
- if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true) ||
- iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false) ||
- val2)
- break;
-
- /* Wait about 20 msec for power gating to disable and retry. */
- msleep(20);
- }
-
- /* restore */
- if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true) ||
- iommu_pc_get_set_reg(iommu, 0, 0, 8, &save_src, true))
+ if ((iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true)) ||
+ (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false)) ||
+ (val != val2))
goto pc_false;
- if (val != val2)
+ /* restore */
+ if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true))
goto pc_false;
pci_info(pdev, "IOMMU performance counters supported\n");
--
2.30.1
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